The invention relates to a modular joint prosthesis having a shaft part insertable into a tubular bone and a head part, adjoining the shaft part, and having a joint connection element, the longitudinal axes of the shaft part and joint connection element forming an obtuse angle.
Shaft prostheses of this kind are produced in various shapes and sizes, to assure that the needs of a given patient can be optimally met.
International Patent Application WO 85/05027 discloses an artificial joint system, in particular a hip joint prosthesis for cementless implantation, which has a shaft part that can be introduced into the upper thigh of the patient and a joint connection element connected to this shaft part. In the proximal region of the shaft part, a threaded sleeve is provided, into which the joint connection element is screwed; the longitudinal axis of the shaft part and the longitudinal axis of the joint connection element are inclined relative to one another. Accordingly, the joint connection element has a threaded peg, which on its proximal end is connected to a conical shaft part for receiving the ball of the joint. The process of screwing the prosthesis in is concluded once the conical shaft part of the joint connection element rests firmly on the proximal region, prepared for the implantation, of the upper thigh bone.
However, the above-described version has the disadvantage that only a complete replacement of the joint, including the ball of the joint, can be done with it.